9/22/2009

Nuclear - Greener Than Wind/Solar? - Part II

One of the long standing arguments against the use of nuclear power has about what to do about the spent fuel, also called nuclear waste. For many years those against nuclear power have made the claim that the large amounts of waste were dangerous and there was no place safe to store it or sequester it for the time required to ensure it was safe. (Plutonium, one of the byproducts of fission, has a half-life of 25,000 years.) People argued the waste could be stolen by terrorists to make a nuclear weapon.

After fuel rods have spent a few years inside a nuclear reactor producing energy, they are removed from the reactor and placed in a cooling pool, held there until they have cooled to the point where they can be removed and placed into storage casks. 'Spent' fuel rods have used only a moderate percentage of the recoverable energy in the fissionable fraction of uranium that makes up the fuel. Each fuel rod assembly contains two different isotopes of uranium: U235, the fissionable isotope, and U238 which is not fissionable. The amount of U235 versus U238 is about 3% to 97%, meaning U235 makes up only 3% of the uranium in the assembly. After being used in the power reactor that ratio has changed, with the fraction of U235 being smaller, as is also the case of the U238. But now there's also a fraction of Pu239, or plutonium, as well as a few other radioisotopes.

At this point the spent fuel is supposed to be stored away someplace 'safe' for the next 25,000 years, something that really isn't practical. But that's what we're supposed to be doing with it. At this point it's considered waste. But is it really?

So is this material "waste"? Absolutely not. Ninety-five percent of a spent fuel rod is plain old U-238, the nonfissionable variety that exists in granite tabletops, stone buildings and the coal burned in coal plants to generate electricity. Uranium-238 is 1% of the earth's crust. It could be put right back in the ground where it came from.

Of the remaining 5% of a rod, one-fifth is fissionable U-235 -- which can be recycled as fuel. Another one-fifth is plutonium, also recyclable as fuel. Much of the remaining three-fifths has important uses as medical and industrial isotopes. Forty percent of all medical diagnostic procedures in this country now involve some form of radioactive isotope, and nuclear medicine is a $4 billion business. Unfortunately, we must import all our tracer material from Canada, because all of our isotopes have been headed for Yucca Mountain.

What remains after all this material has been extracted from spent fuel rods are some isotopes for which no important uses have yet been found, but which can be stored for future retrieval. France, which completely reprocesses its recyclable material, stores all the unused remains -- from 30 years of generating 75% of its electricity from nuclear energy -- beneath the floor of a single room at La Hague.

So why aren't we doing likewise?

Politics.

We have the means to reprocess fuel, which in the process would reduce the total volume of spent fuel tremendously. Instead we put it in storage casks and in cooling pools because of a decision made back in 1975 by President Gerald Ford to stop fuel reprocessing. His executive order was issued because of the fear terrorist would steal the spent fuel and make a bomb. Ford's successor made the order permanent, which is surprising considering President Carter had been a nuclear engineer in the US Navy.

If anyone has ever seen how fuel is stored and how it's transported, those fears would be greatly reduced. Moving that stuff isn't easy, isn't fast, and would be very difficult to steal (and not because of the security but because of the sheer size of the transport casks). If terrorists want nuclear weapons it's easier for them get it from a renegade regime or buy it on the arms market. It's not likely they'd be able to process the fuel themselves in their garage or basement and turn it into weapons grade material.

When all is said and done, the amount of energy it's possible to generate using nuclear power is incredible, Wen one takes into account the total energy cycle, meaning the amount of carbon dioxide created for the planning, construction, commissioning, operation, and eventual decommissioning and dismantling of a nuclear power plant versus alternative energy sources, meaning solar and wind, nuclear is far greener. Nuclear power is such a dense energy source, generating far more electricity than any wind farm or solar farm while taking up a small fraction of the space of either of those alternatives.

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